While Lyme easily holds the title of most common tick-borne illness in the United States, two other diseases, babesiosis and human granulocytic ehrlichiosis (HGE), are spread by the same ticks that transmit Lyme. A 2003 study found that 4 percent of patients with confirmed cases of Lyme disease were also infected with babesiosis or HGE. Contracting two of these at once may increase the severity of symptoms. Rocky Mountain spotted fever (found mostly in the Southeast, despite its name) also spreads through tick bites.

Condition: Babesiosis

Symptoms: May be symptom-free, or can have flulike symptoms: fever, chills, fatigue, sweats, headache, and muscle pain. Gastrointestinal problems, shortness of breath, and dark urine may also occur.

Treatment: An antibiotic accompanied by another drug (typically clindamycin with quinine sulfate)

Condition: Rocky Mountain Spotted Fever

Symptoms: Sudden fever, severe headache, muscle pain, confusion, and a spotted rash, often on the palms and soles of the feet; can be fatal in rare cases

Lyme disease may be the nation's #1 wilderness health threat, but it's no reason to avoid the outdoors. Check out this special report on tick-borne illness to learn how to protect yourself and your family.